1. Field of the Invention
This invention relates to armor comprising layers of energy absorbing fabric sewn together with thread which breaks at multiple locations when the armor is struck by a projectile. More particularly, the invention relates to armor made of polyaramid fibers woven into multiple plies of cloth which are sewn together with relatively weak nylon thread, said thread forming multiple break-away stitching extending in pattered array over the armor surfaces.
2. Brief Description of the Prior Art
The use of polyaramid fibers for personal armor is well known. To shape the armor into a garment, fabric of woven polyaramid fibers is cut into panels, and the fabric panels are sewn together to form the garment. Thread, including nylon thread, has been used to stitch together the fabric panels. The nylon thread being used to form connections between fabric panels was relatively strong in order to withstand stresses thereon encountered when the person wearing the armor moved his arms and/or torso during normal physical activities. There is no suggestion in the prior art that relatively weak nylon thread has been employed to provide breakaway stitches in a patterned arrangement on fabric panels in a body armor garment.
Armor is sometimes designated as "soft armor" when it is in the form of a vest for protection against low-energy threats such as bullets from hand guns. The fabric in such soft armor configurations, especially KEVLAR.RTM. fabric (registered trademark of Du Pont Company) was often treated with chemicals to make it water-resistant. This was necessary to prevent deterioration of performance when the vest or other soft armor became wetted.
Problems have existed in the use of such armor in defeating higher energy threats. To defeat such threats, it was necessary to increase the number of plies of polyaramid cloth. This lead to the problem of excessively heavy or bulky vests, which restricted the actions of the wearer, or made the wearer hot or tired, or both. Thus, there still has been a need for an armor system using layers of fabric, wherein weight and bulk could be reduced by using fewer layers of fabric.
U.S. Pat. No. 4,522,871 to Armellino, et al., discloses a ballistic fabric comprising a multiplicity of fabric plies formed of woven aramid fibers. Criss-crossed rows of stitches are sewn through the fabric plies in a square pattern, as shown in FIG. 1 of the patent drawing. The stitching thread used is preferably the same aramid fiber used in weaving the cloth plies. At column 4, line 35 of this patent, it is stated that the stitching is for the purpose of improving ballistic performance of the multi-ply fabric, particularly against projectiles fired obliquely against the fabric surface. Apparently, the stitching holds the fabric plies relatively close together, with minimal spacing between adjacent plies, whereby the obliquely moving projectile is less able to pick its way through the fabric plies.
The apparent objective of the criss-crossed stitching in the arrangement of Pat. No. 4,522,871 is permanently to connect the various fabric plies together, thus to maintain minimum spacing of the plies at all points along the fabric areas.